The magnitude of vector $ \vec{v} $ is $ \| \vec{v} \| = 2 $ .
To find magnitude of a vector $ v=(a,b) $ we use formula $ ||v|| = \sqrt{a^2+b^2} $
In this example $ a = 2 $ and $ b = 0 $, so:
$$ ||v|| = \sqrt{ 2^2 + 0^2 } = \sqrt{ 4 + 0 } = \sqrt{ 4 } = 2$$